Stairlift skate

ABSTRACT

A skate for a stairlift chair assembly (10) comprises two spaced-apart pairs of rollers, the two rollers (e.g., 27, 28) of each pair being arranged to run respectively above and below a circular section support rail (12) of the stairlift. The two rollers of each pair are rotatable about respective axes (C, D) transverse of the skate, and each roller is able to turn about a further axis (E) which intersects and is orthogonal to the rotary axes (C, D) of the pair of rollers. Each roller is constrained so that its rotary axis (C or D) remains substantially in a plane to which said further axis (E) is perpendicular.

The present invention relates to stairlifts and more particularly to askate for supporting a chair assembly on and guiding it along astairlift rail.

Stairlifts comprise a rail mounted along a flight of stairs, and amotorised chair assembly for travelling along that rail. The chairassembly is supported on the rail by means of a carriage or skatemounted to the chair assembly, and typically comprising two spaced-apartsets of rollers. A known stairlift comprises a flat rail on which therollers run, and each set of rollers is able to turn to followvariations in the inclination of the rail and also to follow curvesformed in the rail according to changes in direction of the stairway.

However, a preferred form of rail is a tubular rail of circularcross-section, which is stronger than a similarly-dimensioned flat railand can be formed to a smaller bend radius.

We have now devised a skate for the chair assembly of a stairlift, inwhich a tubular support rail is used, the skate being able to followcurves in that rail.

In accordance with the present invention, there is provided a skate fora stairlift chair assembly, the skate comprising two spaced-apart pairsof rollers, the two rollers of each pair being arranged to runrespectively above and below a circular-section support rail of thestairlift, the two rollers of each pair being rotatable about respectiveaxes transverse of the skate, and each roller being able to turn about afurther axis which intersects and is orthogonal to the rotary axes ofthe pair of rollers, but being constrained so that its rotary axisremains substantially in a plane to which said further axis isperpendicular.

In use of this skate, each pair of rollers is able to turn, about saidfurther axis or axis of turning, to follow curves in the support rail.However, the rotary axes of the rollers remain substantially inrespective planes, so that one roller of each pair continues to run onthe upper side of the rail, and the other roller of that pair runs onthe lower side of the rail: this ensures a firm support for the chairassembly at all times. In particular, it will be appreciated that therotary axes of the two rollers of each pair remain in respective planeswhich are parallel to each other, said axis of turning beingperpendicular to those planes: in other words, the rollers do notdisplace around the longitudinal axis of the main rail.

Each roller may have bearing elements at its opposite ends (e.g. ballbearings engaged in respective depressions at its opposite ends), thesebearing elements being engaged in arcuate slots of opposed bearingsupports. These bearing elements thus provide for the roller to rotateon its rotary axis, and the bearing elements can slide within theirrespective arcuate slots for the roller to turn on said axis of turning.

In an alternative arrangement, each roller is rotatably mounted on anaxle, the opposite ends of which are fitted with cross-pieces havingarcuate outer end surfaces, these cross-pieces being engaged in arcuateslots of opposed bearing supports.

Preferably the two pairs of rollers are mounted to respective rollerhousings, and the roller housings are mounted for turning aboutrespective parallel, horizontal axes spaced apart longitudinally of theskate. Each roller housing is thus able to turn and follow the supportrail, as the inclination of the support rail changes.

Also in the embodiments to be described herein, the axis of one of theroller housings is fixed, and the other roller housing is mounted on asupport which is able to turn about the axis of the one roller housing:the skate is therefore able to follow variations in the inclination ofthe support rail whilst maintaining the chair assembly upright.

Embodiments of the present invention will now be described by way ofexamples only and with reference to the accompanying drawings, in which:

FIG. 1 is a side elevation of a chair assembly of a stairlift, shownmounted on its support rails;

FIG. 2 is a view of a skate mounted to the chair assembly;

FIG. 3 is a sectional plan view of the skate, showing alternativearrangements for mounting the skate rollers;

FIG. 4 is an exploded view of one of the rollers; and

FIG. 5 is another view of the skate.

Referring to FIG. 1, there is shown a stairlift comprising a chairassembly 10 supported on and guided along a main tubular rail 12 ofcircular cross-section, by means of a skate 20 which will be describedin detail below. The chair assembly 10 is propelled by an electric motor(not shown) which drives a toothed wheel 13 engaged with a correspondingrack 14 extending behind a second or auxiliary tubular rail 15. A roller16 is provided on the motor drive shaft and runs on the upper side ofthe second rail 15 to provide auxiliary support for the chair assemblylo: a further roller 17 runs along the front of the rail 15 to helpprevent the chair assembly 10 from tipping forward.

Referring to FIG. 2, the skate 20 comprises a support member 22 which ispivotally mounted to the chair chassis 19, for turning about ahorizontal, transverse axis A. Two roller housing 24,26 are pivotallymounted to the support member 22, for turning about the axis A and abouta parallel axis B, respectively. Two rollers e.g. 27,28 are rotatablymounted in each of the roller housings: as shown in FIG. 1, one rollerof each pair runs on the upper side of the tubular rail 12, and theother roller of the pair runs on the lower side of the rail. Each rollerhas a concave peripheral surface, of radius of curvature correspondingto the cross-section of the rail 12.

Typically a flight of stairs may include landings or other features suchthat the angle of inclination of the main rail 12 varies along itslength. The spacing of the rail 15 from the rail 12 is therefore variedalong the length of the stairway to ensure that the chair assembly 10remains upright at all positions along the stairway: it will beappreciated that there is a constant distance between the point on themain rail 12 at which the upper pair of skate rollers engage that rail,and the point on the lower or auxiliary rail 15 at which the rollers16,17 engage that rail; thus by appropriately varying the distance ofauxiliary rail 15 from the main rail 12 as the inclination of the mainrail varies, the chair assembly is maintained upright as it travelsalong its rails. Further, as the inclination of the main rail 12 varies,the chair assembly remaining upright, the lower roller pair 27,28 followthe rail 12 and the support member 22 of the skate correspondingly turnsaround the axis A. It will further be appreciated that as theinclination of the main rail 12 changes, each of the two pairs of skaterollers can independently follow those changes, their housings 24,26independently turning about their respective axes A, B.

Typically the stairway will include changes in direction or otherfeatures, such that the main rail 12 will include curved portions tofollow those changes. The skate rollers are able to pivot, as shown inFIG. 3, to follow such curves in the main rail 12. As shown in FIG. 1,the rollers of each pair are mounted for rotation around respective axesC, D which extend transverse to the skate (and normally horizontally):in order to follow curves in the main rail 12, the rollers are able toturn about an axis E which is orthogonal to and intersects both rolleraxes C, D. However, the rollers are constrained so that their rotaryaxes C, D remain substantially in respective parallel planes, to whichthe axis E is perpendicular: axis E lies in a vertical plane containingthe axis of the main rail 12 and is perpendicular to the latter axis.

Referring to FIG. 3, this arrangement may be achieved using one-piecerollers, each roller e.g. 30 having a part-spherical depression in itsopposite ends, receiving respective ball bearings 31: these ballbearings are in turn engaged in arcuate slots 32 in opposed bearingsupports 33,34 of the respective roller housing. The depressionsreceiving the ball bearings 30 are aligned on the rotary axis of theroller, such that the ball bearings 31 provide bearings for the rollerto rotate on its axis. The ball bearings 31 are able to slide within thearcuate slots 32 and so allow the roller to turn on the axis E through alimited angle, to follow curves in the main rail 12: however, it will beappreciated that the axis of rotation of the roller is maintained withina plane to which axis E is perpendicular.

Also as shown in FIG. 3, in an alternative arrangement, each roller e.g.40 is rotatably mounted on an axle 41 having a cross-piece 42 fitted ina transverse slot in each of its opposite ends. As shown in FIG. 4, eachcross-piece 42 has flat, parallel opposite side surfaces and an arcuateouter end surface 43. The two members 42 are engaged in arcuate slots inthe bearing supports 33,34 of the respective roller housing, to allowthe roller to turn through a limited angle about the axis E.

It will be seen from FIG. 5 in particular that each roller is ableindependently to turn around the axis E, although in practice the tworollers of each pair will turn in unison around that axis in order tofollow the main rail 12. FIG. 5 further shows that each roller housingcomprises a base 34 providing a bearing support for both rollers of thatpair, and respective bearing supports 33 for the opposite ends of thoserollers, the bearing supports 33 being mounted to the base 34 by meansof posts 36. It will be noted that the base 34 is cut-away or recessedat 37, to accommodate the main rail 12 where this is tightly curved.

What is claimed is:
 1. A skate (20) for a stairlift chair assembly, saidskate comprising two spaced-apart pairs of rollers, the two rollers ofeach pair being arranged to run respectively above and below a supportrail of the stairlift, said two rollers of each pair being rotatableabout respective axes (C,D) transverse to the moving direction of saidskate, and each roller of each pair of rollers having its opposite endsengaged with respective, opposed support members in a manner such thatsaid roller is able to turn, relative to its support members, about afurther axis (E) which intersects and is orthogonal to the rotary axes(C,D) of said pair of rollers, but is constrained so that its rotaryaxis (C or D) remains substantially in a plane to which said furtheraxis (E) is perpendicular.
 2. A skate as claimed in claim 1, whereineach roller comprises projecting portions at its opposite ends whichengage corresponding arcuate slots formed in said opposed supportmembers.
 3. A skate as claimed in claim 2, wherein each roller hasbearing elements at its opposite ends, engaged in respective saidarcuate slots to provide for rotation of said roller about its axis (Cor D) and to enable the roller to turn about said further axis (E).
 4. Askate as claimed in claim 3, in which said bearing elements compriseball bearings engaged in respective depressions at the opposite ends ofthe respective rollers.
 5. A skate as claimed in claim 2, wherein eachroller includes an axle, the opposite ends of which are fitted withcross-pieces having arcuate outer end surfaces, said cross-pieces beingengaged in respective said arcuate slots to enable said roller to turnabout said further axis (E).
 6. A skate as claimed in claim 1, whereinsaid two pairs of rollers are mounted via their respective, opposedsupport members, to respective roller housings, and said roller housingsare mounted for turning about respective parallel, horizontal axes (A,B)spaced apart longitudinally of the skate.
 7. A skate as claimed in claim6, wherein the axis (A) of one of said roller housings is fixed, theother roller housing being mounted on a support which is able to turnabout the axis (A) of said one roller housing, (24).